In the winding of a yarn, problems always arise if yarn travel is interrupted. There are three possible ways by which yarn travel can be interrupted. First, the feed bobbin may run empty once the trailing end of the yarn has been wound onto the take-up bobbin. The absence of the feed yarn is discovered at the latest whenever an attempt is made to aspirate the yarn end of the feed bobbin for a yarn end joining operation in order to restore yarn travel. The second possibility for yarn interruption is that a so-called yarn cleaner, that is, a sensor for monitoring the yarn quality that has a cutting device, cuts the yarn when a flaw appears in it. After the cut is made, the yarn end upstream of the cut generally is wound onto the take-up bobbin, while the downstream yarn end associated with the feed bobbin is initially clamped in the cutting device until, during the aspiration of the lower yarn by the so-called gripper tube, the cutting and clamping device and a yarn tensioner are opened. The third possibility of interruption of yarn travel is breakage of the yarn because of a yarn flaw. Such a yarn break can occur anywhere in the course of the yarn between the feed bobbin and the take-up bobbin. If a yarn breaks above the cleaner, then as a rule the upstream length of yarn traveling to the take-up bobbin is wound onto the take-up bobbin. The yarn end extending from the feed bobbin is normally aspirated by a so-called catcher nozzle, which is disposed above the cleaner.
To restore the yarn travel, it is known to utilize a suction nozzle which is brought to the take-up bobbin to aspirate the yarn end trailing therefrom, while a catcher nozzle holds the yarn end of the feed bobbin. Both yarn ends are placed in a yarn end joining device for splicing or knotting the two yarn ends in a known manner thereby to restore yarn travel.
If an interruption in yarn travel occurs from one of the three reasons given above, the take-up bobbin is first brought to a standstill in the shortest possible time. Thereafter, the take-up bobbin is again driven for a few revolutions in the windup direction. In this manner, the yarn end trailing from the take-up bobbin will also actually be wound onto the take-up bobbin, particularly in take-up bobbins with a small diameter having a few layers of yarn first wound onto it, whereby the yarn end can later be aspirated by the suction nozzle.
In take-up bobbins that already have a number of layers of yarn and thus a correspondingly larger diameter, it typically occurs naturally that the inertial mass and the large circumference of the bobbin causes the yarn end to be deposited entirely on the circumference of the take-up bobbin as it slows to a standstill.
With heavy bobbins, restarting the winding process requires an increased expenditure of energy. Moreover, it is not advantageous for the yarn layers if a heavy bobbin is again accelerated from a stop, for a brief time and only for a few revolutions, and shortly thereafter is braked to a stop again. Likewise, restarting the winding process for a short time represents a loss of time. Nevertheless, these take-up bobbins are likewise first driven for several revolutions in the winding direction before the yarn end joining operation.
German Patent Document DE 32 25 379 A1 (which corresponds to U.S. Pat. No. 4,535,945) is representative of the above-described state of the relevant art.